Semiconductor lasers are well known and of great importance. One type, which has been explored recently, is a vertical-cavity, surface emitting laser. Such a laser relies on precisely controlled epitaxial growth of semiconducting material of varying composition. A vertical (planar) Fabry-Perot optical resonator is epitaxially formed on the substrate. Two semiconductor multilayer interference mirrors surround an active region. The lasing wavelength is determined by the bandgap of the active region and the distance between the mirrors is set to this wavelength or a multiple thereof. It has further been recognized that the active region can be formed of one or more quantum wells, to which the carriers are confined, thus increasing the lasing efficiency. A quantum well layer is a semiconductor layer of such thinness that its bandgap is determined by both its composition and it thickness. For the AlGaAs and InAlAsP families of III-V materials, these quantum effects occur at thicknesses of 100 nm or less.
However, known vertical-cavity, surface emitting lasers are not completely satisfactory. Much of the reported work has described optically pumped lasers. Optical pumping eliminates the need for metallic or at least highly conducting semiconducting contacts, which tend to absorb light. However, electrical pumping is much preferred for most applications.
Much of the reported work also involves relatively large laser areas. For many applications, only a small quantity of light is required and low power consumption is highly desirable. That is, it is desired that the vertical-cavity laser have a small cross-section. Furthermore, a small cross-sectional cavity provides better directionality and smaller linewidths. Sakaguchi et al have reported in an article entitled "Vertical cavity surface-emitting laser with an AlGaAs/AlAs Bragg reflector" appearing in Electronics Letters, volume 24, 1988 at pages 928 and 929 a laser having a single semiconductor interference mirror and a cavity defined by a surface ring electrode. However, the 20 .mu.m diameter is considered too high.
We have previously reported in an article by Jewell et al entitled "GaAs-AlAs monolithic microresonator arrays" appearing in Applied Physics Letters, volume 51, 1987 at pages 94-96 1.5 .mu.m diameter Fabry-Perot resonators. Recently, we disclosed the optically pumped lasing of such resonators in an article by Jewell et al entitled "Lasing characteristics of GaAs microresonators" appearing in Applied Physics Letters, volume 54, 1989 at pages 1400-1402. Gourley et al have disclosed a similar but laterally undefined lasing structure in a technical article entitled "High-efficiency TEM.sub.00 continuous-wave (AL,Ga)As epitaxial surface-emitting lasers and effect of half-wave periodic gain" appearing in Applied Physics Letters, volume 54, 1989 at pages 1209-1211. We consider the argon ion milling used for the devices disclosed in the two Jewell et al articles to produce excessive trapping at the sides of the pillars. In any case, this art does not disclose the electrical pumping of these narrow devices.
One of us, Jewell, has disclosed in U.S. patent application, Ser. No. 07/317,699, filed Mar. 1, 1989, a vertical-cavity laser structure having one or two quantum wells and two interference mirrors. No details of the procedure to horizontally define the vertical cavity were provided.